This invention relates to an excavator for excavating ground to construct an underground continuous wall, and underground continuous wall construction methods using the excavator in civil engineering and construction works.
In constructing such an underground continuous wall according to a prior art technique, first a hole of an elliptical section having a 2 to 3 m major axis is dug in the ground to a predetermined depth by a powerful bucket or a hole is dug to a predetermined depth by two or three series of auger drills. After the hole formed in slurry is sealed with a bentonite solution to prevent further penetration of slurry, a reinforcing bar cage is placed in the hole and a ready mixed-concrete is then poured into the hole to form a foundation column. Such a method is repeated to form an underground continuous wall.
With the underground continuous wall construction method of the prior art described above, the processes are complicated and hence take much time until the completion of the continuous walls. Moreover, slurry or bentonite solution layers at joints between successive columns interrupt the formation of the continuous wall so that after completion of the wall, ground water tends to leak into the inside of the continuous walls through the joints. It is therefore very difficult to provide the underground continuous wall simultaneously having two functions as a foundation wall and a diaphragm wall.